A wireless communication network typically includes multiple cells having corresponding base stations for exchanging communications with mobile device operating within the cell. The base stations are connected to a centralized system, such as a mobile location center (MLC), for coordinating the communications and interfacing with other networks, such as the public switched telephone network (PSTN) and/or a packet switching network, such as the Internet.
A variety of modern wireless communication services include the feature of determining a geographic location of a mobile device. For example, an emergency service responsive to “911” being initiated at the mobile device includes estimating latitude and longitude of the mobile device in order to locate the device, which is particularly important when a distressed caller is otherwise unable to provide their present location. The geographic location of the mobile device may be determined by a server or other node in the wireless communication network, such as an MLC or a location information server (LIS). The MLC, for example, may determine the geographic location of a mobile device operating within the wireless communication network using positioning measurements from a global navigation satellite system (GNSS) or measurements from a terrestrial positioning system.
Location determinations based on GNSS measurements are generally more accurate than terrestrial measurements, although there are exceptions. For example, GNSS positioning may not be effective in urban environments or indoors, where structures obscure access to multiple satellites, weaken signal strengths, or introduce multi-path components to the signals. Therefore, conventional systems for determining geographic locations of mobile devices typically rely on GNSS measurements, and resort to terrestrial measurements only when GNSS measurements are not available or fail to provide reliable results. Conventional systems may also combine GNSS and terrestrial measurements by requesting and using them in a linear fashion. This approach is time-consuming, and does not necessarily result in the most accurate geographic location determination.
In a representative embodiment, a method is provided for determining a location of a mobile device in a wireless network. The method includes receiving global navigation satellite system (GNSS) measurements for the mobile device, and receiving terrestrial measurements from corresponding transceivers in the wireless network, each terrestrial measurement indicating a distance between the corresponding transceiver and the mobile device. The method further includes selecting at least one terrestrial measurement having an uncertainty value within a predetermined accuracy threshold. The location of the mobile device is determined as a function of the GNSS measurements and the at least one selected terrestrial measurement.
In a representative embodiment, a method is provided for determining a location of a mobile device in a wireless network. The method includes receiving GNSS measurements for the mobile device, and receiving terrestrial measurements from corresponding transceivers in the wireless network, each terrestrial measurement indicating a distance between the corresponding transceiver and the mobile device. The method further includes determining a first dilution of precision (DOP) measure corresponding to the received GNSS measurements, and determining a revised DOP measure corresponding to each terrestrial measurement combined with the GNSS measurements. At least one terrestrial measurement is selected as a function of the corresponding revised DOP measure, and the location of the mobile device is determined as a function of the GNSS measurements and the selected at least one terrestrial measurement.
In a representative embodiment, a method is provided for determining a location of a mobile device in a wireless network. The method includes providing an initial location estimate for the mobile device, the initial location estimate having a corresponding initial uncertainty area, and calculating a minimum range and a maximum range between a transceiver in the wireless network and the mobile device as a function of a given location of the transceiver and the uncertainty area of the initial location. The method further includes receiving GNSS measurements for the mobile device and receiving a terrestrial measurement from the transceiver indicating a distance between the transceiver and the mobile device. The terrestrial measurement is accepted when the terrestrial measurement is between the minimum range and the maximum range. The location of the mobile device is determined as a function of the GNSS measurements and the terrestrial measurement when the terrestrial measurement is accepted.
In a representative embodiment, a method is provided for determining a location of a mobile device in a wireless network. The method includes receiving GNSS measurements for the mobile device and calculating a first location of the mobile device and a first error ellipse at a predetermined confidence level as a function of the GNSS measurements. The method further includes receiving terrestrial measurements from transceivers in the wireless network, each terrestrial measurement indicating a distance between the respective transceiver and the mobile device, and calculating second locations of the mobile device and second error ellipses at the predetermined confidence level as a function of the GNSS measurements and multiple combinations of the terrestrial measurements. The first error ellipse is compared with each of the second error ellipses. The location of the mobile device is determined as either the first location or one of the second locations as a function of the comparison of the first and second error ellipses.